Umbrella



FIG. 1 is a top perspective view of an umbrella showing my new design;

FIG. 2 is a bottom perspective view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a side view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The broken lines depicting the remainder of the umbrella form no part of the claimed design. 

CLAIM The ornamental design for an umbrella, as shown and described. 